Dopamine is a neurotransmitter in the brain. Since this discovery, made in the 1950s, the function of dopamine in the brain has been intensely explored. To date, it is well established that dopamine is essential in several aspects of brain function including motor, cognitive, sensory, emotional and autonomous functions (e.g. regulation of appetite, body temperature, sleep). Thus, modulation of dopaminergic function may be beneficial in the treatment of a wide range of disorders affecting brain functions. In fact, drugs that act, directly or indirectly, at central dopamine receptors are commonly used in the treatment of neurological and psychiatric disorders, e.g. Parkinson's disease and schizophrenia. However, currently available dopaminergic pharmaceuticals may have severe side effects. For instance, dopamine antagonists are known to induce both motor (extrapyramidal side effects; EPS) and mental side effects (e.g. anhedonia, dysphoria, and impairment of cognition), and dopaminergic agonists are known to induce dyskinesias and psychoses (Goodman and Gilman's the Pharmacological Basis of Therapeutics, 9th ed./McGraw-Hill, USA. Chapter 18, p 407-416, Chapter 22, p 509-512, p 515-516).
An approach adopted by many researchers to improve efficacy and reduce side effects of dopaminergic pharmaceuticals, is to develop novel dopamine receptor ligands with selectivity at specific dopamine receptor subtypes or with regional selectivity. Yet another class of compounds acting through the dopamine systems of the brain are dopaminergic stabilizers, which have shown to be useful in the treatment of both neurologic and psychiatric disorders (A. Ekesbo, PhD Thesis, Uppsala University, Sweden: Functional consequences of dopaminergic degeneration; clinical and experimental studies using a novel stabilizer of dopaminergic systems: Ekesbo et al, (−)-OSU6162 inhibits levodopa-induced dyskinesias in a monkey model of Parkinson's disease, Neuroreport, 8, 2567, 1997; Tedroff et al. Long-lasting improvement in motor function following (−)-OSU6162 in a patient with Huntington's disease. Neurology, 22; 53:1605-6, 1999; Gefvert O. et al, (−)-OSU6162 induces a rapid onset of antipsychotic effect after a single dose. A double-blind placebo-controlled pilot study. Scandinavian Society for Psychopharmacology, 41st Annual Meeting, Copenhagen Denmark Nordic Journal of Psychiatry 54/2 93-94, April 2000: Carlsson et al, Annu. Rev. Pharmacol. Toxicol., 41, 237, 2001; Carlsson et al. Current Medicinal Chemistry, 11, 267, 2004).
Another dopaminergic compound, which has been referred to as a dopamine-serotonin system stabiliser, as well as a partial DA D2 receptor agonist, is the recently launched antipsychotic compound aripiprazole (Burris et al, Pharm. Exp. Ther, vol. 302, 381, 2002.). Furthermore, compounds referred to as dopaminergic stabilizers have been described in WO01/46145, WO01/46146, Pettersson et al. The development of ACR16. A new class of dopaminergic stabilizers. Society for Neuroscience 32nd Annual Meeting, Abstract 2002, Vol. 28 part 1 1028, Orlando USA 2002; and Nyberg et al Efficacy and tolerability of the new dopamine stabiliser ACR16 a randomised placebo-controlled add-on study in patients with schizophrenia 12th BIENNIAL WINTER WORKSHOP ON SCHIZOPHRENIA, 7-13 Feb. 2004, Davos, Switzerland.
The typical pharmacological effects that are characteristic for dopaminergic stabilizers as described in WO01/46145, WO01/46146 and Pettersson et al. 2002 can be summarized as: 1) Increased turnover of dopamine in the terminal areas of the ascending dopaminergic projections of the mammalian brain; 2) No or only weak behavioural effects in otherwise untreated rats; and 3) Inhibition of behavioural effects induced by psychostimulants or psychotomimietic compounds in the rat. In the present invention this is referred to as a dopaminergic stabilizer profile.
It is known that certain pharmaceutically active compounds which are used in the treatment of neurological and psychiatric disorders (especially antipsychotic and antidepressant compounds) may have undesirable effects on those cardiac potassium channels which are involved in the electric repolarisation of cardiac cells, commonly referred to as hERG channels (human ether-a-go-go related gene encoded voltage-de-pendent potassium channel) or IKr (rapidly activating delayed rectifier potassium current) channels. Drugs which block these channels can induce ventricular arrhythmia (Torsade de Pointes, TdP), leading to sudden death in otherwise healthy subjects. Indication that a drug might have undesirable effects on cardiac repolarisation is seen through prolongation of the QT interval of the electrocardiogram, which is considered to be a surrogate marker for risk of TdP. A number of drugs have been withdrawn from the market due to unacceptable side effects relating to cardiac arrhythmia (I. Cardiovasc. Electrophysiol. 15, 475, 2004; Eur. J. Pharm., 450, 37, 2002; Cardiovascular Research, 58, 32, 2003)
This invention relates to the field of treatment of mammals suffering from CNS disorders in which the symptoms can be affected by dopaminergic functions, where the treatment comprises administering to said mammal an amount of a new type of compound, with a dopaminergic stabilizer profile. In addition, the compounds display low affinity at cardiac potassium channels, reducing the risk of serious cardiac side effects.